Extensometer



Oct. 10, 1950 T. F. REED EXTENSOMETER Filed June 2a, 1946 m, w m w mmfifi E K m w W Patented Oct. 10, 1950 UNITED STATES PATENT OFFICEEXTENSOMETER Thomas F. Reed, Mount Lebanon, Pa., assignor to UnitedStates Steel Corporation of Delaware, a corporation of DelawareApplication June 28, 1946, Serial No. 679,916

. 3 Claims.

This invention relates to an extensometer and more particularly for anextensometer used to measure the percent extension in temper rolling. Intemper rolling sheet steel it is desirable to cold reduce the stripsufilciently to knock out the yield point, but the extension for thispurpose should be kept as low as possible in order to minimize workhardening. In order to exceed the minimum extension as little aspossible, it is necessary to provide means for accurately measuring theextension so that it can be controlled. Many devices have been proposedfor this purpose, but none have proved entirely satisfactory for variousreasons.

It is a object of my invention to provide an extensometer which issimple and accurate.

This and other objects will be more apparent after referring to thefollowin specification and attached drawing, in which the single figureis a schematic view of the extensometer of my invention as applied to atemper rolling mill.

Referring more particularly to the drawing, the reference numeral 2indicates an uncoiler from which the strip S is uncoiled. The uncoiledstrip passes over an idler or "bi1ly roll 4 into the work rolls 6 of atemper rolling mill which is provided with back up rolls 8 for the Workrolls 6. After passing through the work rolls 6 the strip S passes over"billy roll l and is coiled on the coiler l2. The peripheral speed ofrolls 4 and II] are substantially the same as the speed of the stripover these rolls so that the peripheral speed of the roll [0 will begreater than that of roll 4 by an amount directly proportional to theextension. Two identical generators l4 and [6 are connected to be drivenby rolls 4 and I0, respectively. The characteristics of generators l4and I6 are such that their voltage output increases directly inproportion to their speed so that they have a straight line speedvoltage characteristic. The voltage V2 from generator I6 is appliedacross the fixed side of a potentiometer and the voltage V1 fromgenerator I4 is applied across the variable side of the potentiometer.The potentiometer has a fixed resistance R1 and a variable resistanceR2. The ratio of R1/R2 can vary from 0 to any predetermined value. Inother words, the resistance R1 may be omitted, but it is not desirableto do so since the Working range would then take up only a smallpercentage of the indicating scale. A selfbalancing device I8 isarranged in the variable side of the potentiometer for actuating aslider 20.

I6 also varies. This causes the self-balancing device l8 to move theslider 20 in the proper direction to balance Vi against some fraction ofV2. The self-balancing device l8 may be of any standard make such as theBrown Electronik or the Leads Northrup Micromax. An indicator (notshown) is associated with the self-balancing device I8 and will becalibrated as follows:

Let Y1=strip speed on entering side of work rolls. Y2=strip speed onexit side of work rolls. D1=diameter of roll 4. Dz=diameter of roll [0.S1=angular speed of roll 4. S2=angular speed of roll 10. X=fraction ofR2 to right of slider contact. E=per cent extension of strip in temperrolling. K=constant If the roll diameters are made equal, Equation 12becomes:

For example, if the percent extension E varies from 0 to 10% as X variesfrom 0 to 1.00, the values of X=1.00 and E=10% may be substituted inEquation 13 to obtain:

Substituting this value of B in Equation 13, the scale calibration isfound to be While one embodiment of my invention has been shown anddescribed it will be apparent that other adaptations and modificationsmay be made without departing from the scope of the following claims.

I claim:

1. An extensometer for determining the elongation of strip passingthrough a reducing machine which comprises a generator driven at a speedproportional to entering strip speed, an identical generator driven at aspeed proportional to exit strip speed, a resistance in series with thesecond named generator, a slider in series with the first namedgenerator and part of the said resistance for varying the amount of saidresistance in series with the first named generator, and aself-balancing device in series with the slider for moving said sliderto balance the voltage output of the first generator against a fractionof the voltage output of the second generator to determine the percentelongation.

2. An extensometer for determining the elongation of strip passingthrough a reducing maancing device in series with the slider for movingsaid slider to balance the voltage output of the first generator againsta fraction of the voltage output of the second generator to determinethe percent elongation.

3. An extensometer for determining the elongation of strip passingthrough a reducing machine which comprises a generator driven at a speedproportional to entering strip speed, an identical generator driven at aspeed proportional to exit strip speed, a potentiometer, the secondnamed generator being connected across the fixed side of thepotentiometer and the first named generator being connected across thevariable side of the potentiometer, a slider, a selfbalancing device inthe variable side of the potentiometer for moving said slider to balancethe voltage output of the first generator against a fraction of thevoltage output of the second generator to determine the percentelongation. THOMAS F. REED.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,039,914 McBane May 5, 19362,051,018 Umansky Aug. 11, 1936 2,248,504 Kenny July 8, 1941 2,447,208Rendel Apr. 17, 1948 2,447,209 Rendel et a1 Apr. 17, 1948

